Detecting Ground Deformation And Assessing Landslide Susceptibility In Qinzhou District Based On SBAS-InSAR Technique

The city of Qinzhou district is located at the juncture of the gully regions in the southern part of the Loess Plateau and West Qingling Mountain of Tianshui City.The mountainous city's altitude runs high to low from northwest to southeast,Most of the regions are in the loess hilly and gully region with the thicker loess,the vertical joints development in the loess.Tianshui City is located at the South-North seismic belt and the Lanzhou-Tianshui seismic belt in China.The faults and folds are active in this area,heavy rain in the summer and autumn of the year,the serious geological problems in the country due to the excessive human's activities.Geological hazards such as landslides,mudslides,and collapses,It caused huge economic losses and security threats to urban residents,especially in 2008,the“5.12”Wenchuan earthquake and the“7.25”geological disaster in2013 in Tianshui area have caused a large scale mountain disasters,such as the historical landslides revived,potential landslides,dangerous slopes,and land subsidence and other geological disasters occurred.Qinzhou District is facing more serious Landslide hazards.,How to identify and predict the landslide hazards is the challenge.With the rapid development of town construction process,traditional inefficient landslide monitoring,surveys investigating and mapping have been unable to urban construction.In recent years,the application of satellite earth observation technique and landslide susceptibility assessment technique developed quickly,especially the new technologies such as Interferometric Synthetic Aperture Radar(InSAR)and various landslide susceptibility assessment were invented.Moreover,the development of SBAS-InSAR(Small BAseline Subset-InSAR)technique overcomes the limitations of traditional InSAR technique due to time decorrelation and atmospheric delay effects,long term series,high-precision(mm-scale)surface deformation monitoring at the regional scale can be realized.It as been widely used in landslide monitoring.SBAS-InSAR technique and Logistic Regression Model(LSM)to obtain surface deformation monitoring velocity and landslide sensitivity assessment application research in Qinzhou District in this thesis.The main work and results are as follows:(1)The SBAS-InSAR technique was proposed in this thesis based on two kinds of SAR data,ALOS PALSAR and SENTINEL1A,to obtain the surface deformation velocity in the study area from 2007 to 2011 and 2014 to 2017.The most deformation areas are mainly concentrated in the north of the urban area.The maximum deformation rate reaches-34.1 mm/years along the banks of the river and major roads in study area.(2)The SBAS-InSAR technique shows that regional surface deformation velocity,and our field investigations and verifications with large deformation rates in study areas,the result were divided into three types of ground deformation:landslide deformation?unstable slopes and Land subsidence.It has verified the accuracy and practical application value for SBAS-InSAR technique.(3)The logistic regression model(LSM)was proposed in this thesis to evaluate the sensitivity of regional landslides,and combining with the monitoring data of regional surface deformation,to refine the landslide sensitivity assessment results.The new LSM updates the areas of moderate sensitivity,high sensitivity,and very high sensitivity to the original results.And it's area increases by 14.1 km~2,16.35 km~2,and 9.08 km~2 respectively.Finally,the thesis obtained an accurate results of regional landslide susceptibility and improved landslide sensitivity.based on this method.